PROJECTSUMMARY Nicotineaddictionisthelargestcauseofpreventablediseaseanddeathworldwide,andcurrenttreatmentsare onlymoderatelyefficacious.Nicotinicactsonnicotinicacetylcholinereceptors(nAChRs)inthebrain.nAChRs in the ventral tegmental area (VTA) have been shown to mediate the reinforcing properties of the drug, while nAChRsinthemedialhabenula(MHb)-interpeduncularnucleus(IPN)pathwayhavebeenshowntomediatethe aversive properties of the drug. Although studying nAChRs provides an understanding of the direct actions of nicotine,itdoesnotelucidatethefullviewofallthemechanismsinvolved.Therefore,thereisanurgentneedto expandourunderstandingofnicotine?seffectsonthebraintoexaminepotentialendogenousproteinsthatmay mediate these processes as well. The endogenous protein, Lynx1, has been shown to directly interact with nAChRs and is co-expressed with nAChR subunits;? however, Lynx1 has yet to be examined in the context of nicotine reinforcement. Here we propose novel experiments that will characterize Lynx1 in nicotine reinforcement.Todothis,Lynx1knockoutmiceandtheirwildtypelittermateswillbeexaminedforintravenous nicotineself-administrationacrosslow,moderate,andhighdosesofnicotine.Baselinesubunitexpressionwill alsobeassessedbetweengenotypestoexaminethepotentialforcompensationinexperiments.Tounravelthe role of Lynx1 and its colocalization with different nAChRs subunits, Lynx1 knockout mice and their wildtype littermateswillbeexaminedforc-fos,Lynx1,andnAChRsubunitsusingRNAscopeandimmunohistochemistry. Finally,toexaminewhetherLynx1intheVTAmediatesnicotineself-administration,aseparatecohortofwildtype micewillbeinjectedintheVTAwithashRNAvirustoknockdownLynx1.Resultsfromthesestudieswillreveal important insights into factors underlying nicotine reinforcement. Thus, these studies may thereby elucidate a mechanism to provide a foundation for the development of efficacious treatment for nicotine dependence and leadtonovelavenuesforfutureresearchdirections.Moreover,asapredoctoralstudent,theseexperimentswill allow me to expand expertise and skills by learning multiple cutting-edge viral, molecular, surgical, and behavioraltechniques.Thedevelopmentoftheseskillswillpromotemetoachievemycareergoalofbecoming aleadingacademicscientistbymakinganindelibleimpactonthefieldofaddiction.